The present invention relates to microchannel arrays, particularly to the input wells for microchannel arrays for electrophoresis and more particularly to a T-load input well geometry for microchannel arrays and method of fabrication.
Current emerging alternative methods to commercial slab-gel electrophoresis (e.g., for DNA sequencing) are systems based on discrete drift channels. One type is bundles of discrete glass micro-capillaries. Another type consists of one dimensional, integrated arrays of microchannels patterned in bonded glass plate pairs, such as described and claimed in U.S. application Ser. No. 08/772,639 filed Dec. 23, 1996, entitled Micromachined Chemical Jet Dispenser, and assigned to the same assignee. The input sample insertion geometry of the microchannel array prior type of analysis system (e.g., electrophoresis array), involves a right angle connection to the microchannel from the sample input well. This results in a three-dimensional (3-D) injection volume of the sample onto the end of the drift gel in the microchannel, which, in turn, is a fundamental limit of resolution; the gel-loading buffer fluid or sample interface is defined by convection and diffusion and is difficult to control because the input well or hole in the top plate overlaps the microchannel end in the bottom plate. The above-referenced integrated array type system requires fabricating a microchannel groove or bottom plate, and also a macro-hole capping plate; the capping plate completes the microchannel and also must be highly precision drilled for the input/output holes, and also precision aligned to the microchannel bottom plate for glass fusion bonding to assure alignment of the input wells with the ends of the microchannels.
It has been determined that the highest resolution can be obtained with electrokinetic (ek) loading directly onto a plane perpendicular to a micro-capillary axis at its end. Such high resolution could not be accomplished with the right angle connection of the microchannel end to the input well utilized in the prior system. The present invention provides a geometrical solution and method of use to enable loading directly onto a plane perpendicular to the end of the microchannels. Thus the present invention involves a new 3-D input well geometry comprising a T-load for planar, high density, integrated, microchannel arrays. The input well of the present invention also enables two-dimensional (e.g., titer plate format) sample input and efficient parallel operations and minimal input/output port space on the plates. The 3-D input well of the present invention extends past the ends of the micro-channel and partially or completely through the bottom or grooved microchannel plate; one input well embodiment being termed a "blind T-load" with the other input well embodiment being termed a "thru T-load."